Field of the Invention
The present invention relates to a fuse for a semiconductor configuration having a semiconductor body with two main surfaces running essentially parallel to one another.
As is known, the use of fuses in semiconductor configurations and, in particular, in semiconductor memories is becoming increasingly important. They are used to connect appropriate substitute elements or redundant elements, such as memory cells or word lines, when individual elements fail. If, for example, a word line is found to be faulty when testing a semiconductor memory, then a redundant word line is activated instead of the faulty word line, by disconnecting or blowing fuses. Chip options can also be connected via fuses, for example.
There are now two different ways to disconnect fuses: in the first way, the disconnection is carried out by the action of a laser beam, and this is what is referred to as a laser fuse. In the second way, the disconnection is carried out by electrical destruction resulting from the production of heat; this is an electrical fuse, or E-fuse.
Both fuse types have the common feature that they are produced only in planar form (see, for example, U.S. Pat. Nos. 5,663,590 and 5,731,624). Therefore the contacts of a fuse lie in a plane, which runs essentially parallel to a main surface of the semiconductor body of a semiconductor configuration, that is to say, for example, of a semiconductor memory. Such a structure has first contacts and second contacts, which are each disposed on conductive areas, which are composed, for example, of highly doped silicon. The areas are electrically connected to one another by a fuse, which represents a conductive connection between the areas. The fuse may, for example, be composed of doped polycrystalline silicon, or else of metal. The fuse itself has a fine form, and has a width in the order of magnitude of a few xcexcm down to less than 1 xcexcm.
If a current which is greater than a certain limit value now flows between the contacts, then the fuse is destroyed by the resistive heat produced by the current flow. Therefore, the fuse is blown. The programming voltage is in this case greater than the operating voltage of the chip. The magnitude of the programming voltage is dependent, inter alia, on the width of the fuses.
The process of blowing a fuse can also, of course, be carried out by the influence of a laser beam, and this is particularly expedient when the fuse is located on the surface of a semiconductor configuration.
The fuse together with the associated contacts requires an area that is not negligible on a semiconductor chip. The area required for fuses is a disadvantageous factor in terms of the continuous aim to miniaturize semiconductor configurations. This applies in particular to semiconductor memories, since a large number of fuses are required in them.
It is accordingly an object of the invention to provide a fuse for a semiconductor configuration and a method for its production which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type, which is distinguished by a minimal area requirement; and in order to keep the programming voltage low, it should be possible to set the diameter of the fuse to values which are significantly less than 1 xcexcm.
With the foregoing and other objects in view there is provided, in accordance with the invention, a semiconductor configuration. The semiconductor configuration includes a semiconductor body having a main surface and an insulator layer disposed on the main surface of the semiconductor body and has an upper surface. The insulator layer has a cavity formed therein extending to the main surface of the semiconductor body. A fuse having a fusible part extends from the main surface of the semiconductor body toward the upper surface of the insulator layer at right angles to the main surface of the semiconductor body, and the fuse is embedded in the cavity.
In the case of the fuse for the semiconductor configuration having the semiconductor body with two main surfaces running essentially parallel to one another, the object is achieved, according to the invention, by the fuse extending in the direction between the two main surfaces and being embedded in the cavity in the semiconductor body.
The fuse according to the invention is thus not, like all the existing fuses, disposed in a planar structure. In fact, it is provided in the xe2x80x9cverticalxe2x80x9d direction between the two main surfaces of the semiconductor configuration. This factor on its own achieves a considerable reduction in area, so that it is possible to achieve a considerably improved packing density for semiconductor configurations with fuses. In addition, the diameter of the fuses can be set without any problems to values of considerably less than 1 xcexcm, and this results in low programming voltages.
The enclosure of the fuses in the cavity has a further advantageous effect, which can be achieved only with major complexity and a large space requirement with the previous planar fuses. When the fuses are destroyed, the melt that is produced cannot produce any undesirable short circuits due to vapor-deposited material, since the vapors are reliably enclosed in the cavity. There is therefore no need for any special measures in order to avoid short circuits, which can occur when planar fuses are destroyed. Such measures with existing fuses contain the maintenance of specific minimum distances to adjacent elements or other fuses, or the provision of protective ring structures around the fuses.
A method for producing the fuse according to the invention is distinguished, by method steps which includes applying an insulator layer, which is etched selectively with respect to a semiconductor substrate and is composed, for example, of silicon nitride, is applied to the semiconductor substrate, which is composed, for example, of silicon. The insulator layer and the semiconductor substrate are then anisotropically structured, so that a semiconductor area in the form of a column remains under the remaining insulator layer after structuring. The column-shaped semiconductor layer is then isotropically etched over, in which case the width and electrical characteristics of the fuse can be set without any problems in this step. A dielectric composed, for example, of silicon dioxide is anisotropically applied to the remaining structure, which can be done by vapor deposition, and as a result of which a cavity is formed.
Contact is then made with the fuse that has been produced in the normal way, once again, as well as with its metallization, with subsequent passivation. A buried layer contact may be used if required for making contact, and this contributes to a further improvement in the packing density.
The fuse itself is advantageously composed of doped or undoped silicon. In this case, it may have a length of up to a few xcexcm and a diameter of about 0.1 to 0.5 xcexcm.
At its end facing the semiconductor body, the fuse makes contact, for example, with a buried layer, as has already been explained above, while, at its opposite end, which is located in the vicinity of one main surface of the semiconductor body, a metallic contact can be provided, composed, for example, of tungsten with appropriate contact diffusion. Such a tungsten contact can then be connected to an interconnect composed, for example, of aluminum, tungsten or polycrystalline silicon.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a fuse for a semiconductor configuration and a method for its production, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.